Acoustical distortions in capacitance hydrophones and the effect of diaphragms in measurements of shock wave pulses

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Authors

  • L. FILIPCZYŃSKI Department of Ultrasound, Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland
  • J. ETIENNE Department of Ultrasound, Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland
  • T. KUJAWSKA Department of Ultrasound, Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland
  • J. WÓJCIK Department of Ultrasound, Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland
  • B. ZIENKIEWICZ Department of Ultrasound, Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland

Abstract

The shock wave pulse measured by means of a membrane PVDF hydrophone was compared with the pulse obtained by means of the capacitance hydrophone showing distortions in the pulse trailing edge. The mechanism of distortions in the capacitance hydrophone was explained and confirmed by experiments as caused by transverse waves generated on the surface of the hydrophone's metal plate by compressional incident waves. The effect of the rise time of the measured shock wave pulses was interpreted and analysed by means of diaphragms with various apertures. Interaction of the applied diaphragms with the measured acoustic fields was explained showing their equivalence to the high pass filtering. The differentiating circuit used for determination of the particle velocity from the displacement, measured by the capacitance hydrophone, was analysed. Also an improved capacitance hydrophone was applied in measurements.

References

[1] E. DIEULESAINT, D. ROYER, Ondes elastiques dans les solides, p. 36, Masson et Cie, Paris 1974.

[2] J. ETIENNE, L. FILIPCZYŃSKI, T. KUJAWSKA, B. ZIENKIEWICZ, Electromagnetic hydrophone for pressure determination of shock wave pulses, Ultrasound in Med. and Biol., 23, 747-754 (1997).

[3] L. FILIPCZYŃSKI, Absolute measurements of particle velocity, displacement or intensity of ultrasonic pulses in liquids and solids, Acustica, 21, 173-180 (1969).

[4] L. FILIPCZYŃSKI, Measurements of longitudinal and transverse waves radiated by a compressional source into elastic semispace, Proc. Vibr. Probl., Warsaw, 5, 89-93 (1964).

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